1. Field of the Invention
This invention relates to multiplexing techniques for obtaining status of a plurality of switches disposed at a remote location in the form of a matrix keypad and connected to a controller by a single wire bus and, more particularly, in a preferred embodiment to systems for generating visual displays at a remote instrument panel indicative of the status of each switch of the matrix, the switches being separately scanned by a switch scanner that connects at a single point to the single wire bus and controlled by a remote microcontroller.
2. Description of the Prior Art
Scanning matrices of switches or keys of a keypad has generally been done by microcomputers or controllers using complex software. Where separate keyboards are employed, a serial link between the controller and the keyboard usually improves reliability and saves on cable usage but further complicates the protocol between devices.
In an effort to place a matrix of switches at a remote location and use a minimum number of wires between the controller and the matrix, a search was initiated for a scheme that would use as few as a single wire between devices. That search resulted in the improved matrix scanner system of the present invention.